Posted by Tom on .
Which of the following is NOT true about the thermodynamic standard state?
A. A solid is in its standard state when the atmospheric pressure is 1.00 atm and the temperature is 25C.
B. A pure liquid is in its standard state at 25C and a vapor pressure of 1.00 atm.
C. An aqueous solution is in its standard state at a concentration of 1.00 M.
D. A gas is in its standard state when its pressure is 1.00 atm and its temperature is 25C.
E. All of these are true.
I am left between B and C. For B i couldn't find the VP of water to be 1.00atm. I don't know anything about C.
C is correct. 1 M concn is the standard state for solutions. B is not true. A pure liquid need NOT have a vapor pressure of 1 atm. If it's a pure liquid, then it has its normal vapor pressure at 25 degrees C.
Some notes here, which probably were not meant to apply to this problem but may be worth mentioning, anyway, are as follows:
The concn of 1.00 molar ACTUALLY is an ACTIVITY of 1.00.
I understand that the IUPAC changed the standard pressure from 1 atmosphere to 1 bar (exactly 100 kPa) in 1990. As far as I know, most everyone in the US still uses 1 atm. That sorta like the STP and SATP. SATP haven't caught on in the US yet, at least not widely.
Under those added rules, there are several statements above not true; however, I think the question was meant to be more elementary than that.
If nitrogen gas is 0.10 atm, hydrogen gas is 0.50 atm, and oxygen gas is 1.00 atm. What is the partial pressure of the three gases?